1. Field of the Invention
Exemplary embodiments of the present invention relate to an accelerator pedal and/or brake pedal for a vehicle and, particularly, to an active eco pedal apparatus which can control ON/OFF of a pedal in a single-phase control manner to eliminate a factor contributing to increasing its costs, and can eliminate cogging torque to prevent deterioration of a pedal feeling when an eco mode is activated.
2. Description of Related Art
Among various methods of improving fuel efficiency of vehicles, a method of reducing unnecessary manipulation of a pedal is widely known.
As one example of the method of reducing the unnecessary manipulation of the pedal, there is a method of reducing the number of manipulation of an accelerator pedal, in which an operation mode is set to allow a driver to feel a different stepping force depending upon driving conditions. That is, the driver stepping on the accelerator pedal feels absolutely different pedal reaction to reduce the number of manipulation of the accelerator pedal.
This operation mode is generally referred to as an eco mode, and a pedal employing the eco mode is referred to as an eco pedal.
That is, the pedal reaction felt by the driver in a normal mode is provided by a resilient deformation of a spring, while in the eco mode the drive stepping on the pedal is provided with another reaction generated from a separate power source when a specific driving condition of the vehicle is satisfied.
In the eco mode, since the driver feels the pedal reaction different from that provided by the spring, the driver reduces the number of the unnecessary manipulation of the accelerator pedal, thereby improving the fuel efficiency.
As one example of the eco pedal capable of allowing the driver to feel the separate reaction, there is a power method employing an actuator. In this instance, a common PMDC type motor is utilized, and the power of the motor is converted through a reduction gear including a worm gear and a worm wheel to activate the eco mode.
In the case of the PMDC type motor, however, since the reduction gear is inevitably employed between a motor and a pedal to transmit the power, it has a quality problem caused by the high loss of power transmission and a problem of operational noise generated by a complicated power transmitting path.
Meanwhile, if a linear type motor is applied to the actuator, it is possible to remarkably improve the above-problems contained in the PMDC type motor, that is, the high loss of power transmission and the operational noise generated by the complicated power transmission path.
The reason is that since the power is transmitted by a magnetic field generated from the linear type motor, there is no loss of power transmission and no operational noise generated by the operation of the reduction gear.
As compared with the PMDC type motor, the linear type motor improves the quality, without generating the operational noise, as well as improves the accuracy of the operation.
As described above, the eco mode is a manner of providing the driver with the pedal reaction against the stepping force generated when the driver pushes down the pedal.
To this end, the linear type motor includes a movable member which is linearly moved with respect to a stator using the electric field generated when the current is supplied to the motor. Since the pedal is pushed by the movable member, the driver stepping on the pedal feels another reaction, so that the driver can take his or her foot off the accelerator pedal.
If the motor is controlled in a three-phase control manner, the motor should have a three-phase driver chip for driving the motor, a field effect transistor (FET) for detecting an overload of the current applied to the motor, and a hall sensor having a hall element for detecting a stroke of the motor.
Therefore, since the eco pedal utilizing the linear type motor which is controlled in the three-phase control manner is provided with the three-phase driver chip, a plurality of FETs, and a plurality of hall sensors, it is disadvantageous in view of the costs.
In particular, in addition to the expensive three-phase driver chip necessarily required for the motor control, since at least six FETs should be provided, it causes the costs to increase.
Further, since the hall sensors are provided on at least three positions, an error possibility will be disadvantageously increased. The reason is that the operation reliability of the hall sensor generating an electric signal is not stable, and the motor does not operate basically at the time of electrical failure.
In the linear type motor, since the thrust is varied by a stroke-based current control using the hall sensor and alternative arrangement of continuous N, S, N and S magnets, as shown in FIG. 8A, cogging torque which is a force such as weak vibration is relatively high.
Therefore, according to the eco pedal employing the linear type motor having the relatively high cogging torque, when a reaction stepping force is created by hysteresis in the eco mode, the relatively high cogging torque deteriorates the driver's pedal feeling over the whole range, which is unfavorable for the pedal feeling.